Mercury switch



Sept. 4, 1934.

P. K. CRAMBLET MERCURY SWITCH Filed Feb. '23, i926 INVENTOR. Bea/.1, ff.CFAMBLZEY.

Patented Sept. 4, 1934 1,972,291 MERCURY swl'ron Paul K. Cramblet,Milwaukee, Wis'.,,assignor, by

mesne assignments, to ,Minneapolis-Honeywell Regulator Company,Minneapolis, Minn., a corporation of Delaware Application February 23,1926, Serial 19 Claims. (Cl.200--1 52)' This invention relates toimprovements in switches, and more particularly to those of the typeknown in the art as mercury switches.

Switches of this type comprise a hermetically 5 sealed envelope ofglass, electrodes sealed therein and a body of mercury movable in theenvelope so that in one position of the latter the circuit through theelectrodes is completed, whereas when tilted or otherwise moved into aposition in which the mercury may flow out of engagement with theelectrodes, the circuit is broken. Generally speakLng, there are twotypes of these switches now in general use, one employing an envelope ofsoft glass, such as the lead or lime varieties, with the electrodessuspended therein and in such position that they are bridged by the bodyof mercury when the tube is moved into a certain position. In this typeof mercury switch the arcing both at the make and the break of thecircuit has a pronounced deteriorating eifect upon the electrodes, as iswell known, this action on the electrodes affecting them to such extentthat the life of the switch is materially shortened. In the other typeof switch referred to the envelope is made of quartz or hard glass, suchas Pyrex or the like which, as is well known, is substantiallyunaffected by the heat of the arc. .In this type of switch, therefore,owing to the hard glass envelope, the electrodes and mercury may be soarranged that a mercury make and break directly on the surface of theenvelope may be utilized, the electrodes in these switches being usuallyarranged in wells or the like formed in the envelope, or so positionedrelative to one another that each of them is at all times immersed inmercury so that all of the arcing which occurs occurs directly betweenmercury and mercury as the tube is tilted or otherwise moved to make andbreak the circuit. As is well known, a mercury to mercury-make and breakis desirable for a number of reasons. Chief among these is the fact thatin such a switch the electrodes are not subjected to deterioratinginfluences of any kind. Then, too, thearcing is less in a mercury tomercury make and break, as is well known. Furthermore, any arcing whichdoes occur in a switch of this type merely results in a volatilizationof a minute portion of the mercury at the'point of contact whichimmediately condenses upon quenching of the arc and flows .back into themain body again. Despite the many advantages incident, to theutilization of a mercury to mercury contact in switches of thischaracter,they have not come into general use principally because of thecost of the, hard glass and the difficulties encountered in hermeticallysea1--.

ing'the leading-in wires or electrodes into an envelope made of suchglass. r

One of the objects of the present invention, therefore, is to provide amercury to mercury make and break in a switch of the soft glass envelopetype whereby the various disadvantages inherent in-the use of a hardglass envelope may be overcome without sacrificing any of the advantagesof such a construction.

With the foregoing in mind, the invention con- 05 templates amercury'switch comprising a hermetically sealed envelope of any usual orordinary soft glass composition heretofore employed, electrodesprojecting into said envelope and hermetically sealed therein, a body oimercury movable in said envelope to perform the circuit making andbreaking function, together with means for entrapping a portion of thebody of mercury in the vicinity of one of the electrodes and maintainingsuch portion of mercury in contact therewith both when the main body ofmercury is in and out of circuit making position, thus ensuring amercury to mercury make and break upon operation of the switch andcomplete protection for the electrodes against the deterioratinginfluences of the arc.

Other objects and advantages of the invention will be apparent to thoseskilled in the art from a reading of the following specification takenin connection with the accompanying drawing, wherein three forms of theinvention are illustrated.

In the drawing:

Figure 1 is a sectional view, taken through a switch constructed inaccordance with the present invention and in circuit making position;

Fig. 2 is a sectional-view taken on the line 22 of Fig. 1;

Fig. 3'is a sectional view, similar to Fig. 1, illustrating a slightlydifferent form of switch of the type contemplated by the presentinvention; and

Fig. 4 is a longitudinal, sectional view of a third form of theinvention.

Referring more in detail to the drawing, and first to the form of theinvention illustrated in Figs. 1 and 2 thereof, the switch comprises acontainer or envelope, 10 which, as already pointed out, may be formedof soft glass such as the lead and lime varieties. This envelope issubstantially capsule shape provided at its opposite ends with lateralprotuberances 11 through the crowns of which the leading-in wires 12 and13 extend into the interior of the envelope. These leading-in wires maybe of the usual copperclad type and are hermetically sealed in the wallof the envelope as at 14 at their points of projection therethrough. Theelectrodes 15 and 16 arepreferably formed of some wire which is notaffected by the mercury, such, for instance, as iron, nickel, tungsten,or the like. These electrode wires 15 and 16 are welded as at 17 and 18to the leading-in wires 12 and 13 immediately inwardly of 'the seals 14.The movable body of mercury in the envelope bears reference character 19and,.as willbe observed, in one position, or in other words, theposition shown in Fig. 1 of the drawing, this mercury completes thecircuit between the electrodes, whereas, as will be observed, upontilting or oscillation of the envelope into an opposite or reverseposition, the mercury will flow to the other end of the envelope, thusinterrupting the circuit. The envelope of these switches isgenerally-filledwith an inert gas such as hydrogen in order to avoidchemical action and to assist in suppressing the arcing which results inprolonging the life of the switch.

Thus far, the switch described is much the same as switches heretoforedeveloped and which are at the present time .in rather general use, andin which the make and break occurs directly between the electrodes andthe mercury resulting in, the deteriorating effects above pointed out.-

To overcomethe disadvantages inherent in this type of switch heretoforeconstructed andto, in reality, transform the same into a mercury tomercury make and break type of switch, it is proposed, according to thepresent invention, to provide means for constantly, maintaining aportion of mercury around one of the electrodes regardless of themovement of the main body of mercury. In the drawing, this means isshown in the form of a cuplike element 20 having an elongated aperturedsleeve or neck 21 formed integrally therewith or welded thereto andthrough which the electrode 15 extends downwardly into cup 20. Thiscuplike element 20 may be formed either of quartz or some of the variousso-called hard glass compositions so as to render it unaffected by anyarcing which may occur. The

e1ectrode,-of course, need not be sealed in the neck 21, it having beenfound sufiicient to merely pinch or press it around the electrode intogripping or holding position, or in other words, just sufliciently toprovide for the supporting of the cup from the electrode substantiallyas shown. It has been found, in practice, advantageous to tilt the cupslightly so that the open end thereof inclines slightly with referenceto the longitudinal axis of the envelope, and it has also been foundadvantageous to form the openingin the cup of elongated, oval shapesubstantially as shown in Fig. 2, as this'has proved topre'sent a bettercontacting surface of mercury at the mouth of the cup at which point themake and break occurs. As will be observed, a portion of the mercury isentrapped in the cup 20 through-, out all operations of the switch andthus inercury is maintained in contact with the electrode 15 at thispoint. The electrode 16 preferably extends downwardly to a point nearthe lower wallof the envelope and then forwardly along such wall, asshown, this electrode being in the main body of the mercury for alloperations -of the switch. As already explained, the make and breakoccurs at the mouth of the-cup 20, or to be more exact, over the lowerlip of the mouth, and occurs between the mercury in the cupand the mainbody of mercury as it flows towards or away from the cup, depending uponthe direction of oscillation.

. In the switch illustrated in Figure 3, the cup shown'at 30 isreversed, as compared with the cup mounting in Fig. 1, but in otherrespects is substantially the same as the switch shown in Fig. 1, bothin construction and operation, the

mercury to mercury make and break feature being preserved. In Fig. 4,the leading-in wire 40 enters the envelope through the crown of aprotuberance or well 41 formed in the lower wall of the envelope and atsuch point as enables the electrode 42 to be materially shortened as.compared to the corresponding electrodes in Figs. 1 and 3, for instance.This modification is proposed for the handling of higher current values,where it is desirableto have the electrodes as short as possible so asto avoid excessive heating, such as would occur with the use of anelec-'- trode of appreciable length. In other respects, the switch shownin Fig. 4' is substantially the same, both in construction andoperation, as that shown in Fig. 3.

From the foregoing it will be understoodthat through the utilization ofmeans for entrapping a portion of the body of mercury and holding suchportion in constant contact with one of the electrodes, that a switchhas been provided wherein a mercury to mercury make and break isutilized and the resultant advantages thereof obtained, .while stillemploying the ordinary soft glass envelope. It will be further observedthat in the particular construction and arrangement described andillustrated herein, the electrode 15 "is shielded entirely from contactwith the mercury except at its lower end which dips into the cup. Thus,the possibility of a so-called splash contact upon oscillation of theenvelope is provided against, the only contact possible being betweenthe main body of mercury and that entrapped irr the cup 20 and at themouth of the cup which, as already explained, is formed of quartz or ofhard glass so as to be unaffected by any arcing which may occur.

It will also be observed that the point of make and break, namely in themouth of.the cup 20, is sufliciently removed from the adjacent wall ofthe envelope to prevent any injurious or rupturing effect upon thesofter glass composing said envelope. a

It will thus be apparent to those skilled in the art that, through theemployment of means in association with oneof the electrodes formaintaining that electrode in constant contact with a portion'of themercury, and the use of quartz or hard glass in the formation of suchmeans, a

mercury switch employing the ordinary soft glass envelope maybe used tosecure a mercury to mercury make and break and all of the advantagesincident to such a switch without the costliness or the vmanydisadvantages inherent in the mercuryto mercury make and break hardglass envelope type-of switch heretofore employed in the securing ofthese results. The invention, therefore, is chiefly characterized by theprovision of constant mercury coverings for the electrodes in a softglass envelope and the confining of the make and break area, or arcingzone, to a point removed from the walls of said envelope.

'It is intended, therefore, that the invention be broadly interpretedas, of course, it may take many forms other than those illustrated anddescribed, and is subject to many changes and modifications withoutdeparting from the spirit or scope thereof. I Therefora'it is' notdesired to of shocks and stresses between the envelope and limit orrestrict the same except where limitations may appear in the appendedclaims.

The invention claimed is: t

1. A switch of the character described comprising an envelopeof softglass, electrodes sealed therein, a body of mercury movable within saidenvelope, and means for producing a mercury to mercury make and breakintermediate said electrodes upon oscillation of said envelope includinga hard glass mercury containing element separate from theenvelope andfixedly supported upon the envelope in spaced relation thereto andconfining the make and break area or arcing zone to a'point removed fromthe walls of said -envelope.

2. A switch of the class described comprising an outer hermeticallysealed envelope, a movable body of mercury therein, electrodes formaking contact with said mercury, and means for causing said mercury toseparate and reunite at a point intermediate said electrodes and removedfrom the walls of said envelope upon bodily movement of said switch,said means being in the form of a cuplike element fixedly suspended fromone of said electrodes out of contact with the walls of said envelopeand serving to maintain a portion of said mercury in constant engagementwith said electrode to thereby ensure a mercury to mercury contact atthe mouth of said cup upon operation of said switch.

3. The combination with a switch comprising a soft glass envelope, and amovable body of mercury and electrodes sealed therein, of means foreffecting separation of said body of mercury at a point intermediatesaid electrodes and removed from the walls of said envelope uponoperation of said switch, said means comprising an element of arcresisting material fixedly supported within but out of contact with saidenvelope.

4. The combination with a switch comprising a soft glass envelope, and amovable body of mercury and electrodes sealed therein, of means foreffecting separation of said body of-mercury at a point intermediatesaid electrodes and removed from the walls of said envelope uponoperation of said switch, said means comprising an 'element'separatefrom, fixed within but out of contact with said envelope, said elementbeing of a substance capable of withstanding high temperatures and rapidtemperature fluctuations.

' 5. The combination with an electrical contactor comprising a glassenvelope, cooperating electrodes sealed therein, and a body of mercurymovable therein, of a cuplike element surrounding one of said electrodesand adapted to maintain a portion of said mercury in contact therewithirrespective of the movements of the main body of mercury, said cuplikeelement having a sleeve through which its associated electrode extendsand-by which it is supported from said electrode.

6. The combination with a mercury switch comprising an envelope,electrodes and a movable body of mercury sealed therein, of meansassociated with one of said electrodes for entrapping a portion of saidmercury and holding the same 1 arcing'to a zone removed from. the wallsof said envelope whereby the envelope is protected against the action ofarcing and the transmission mouth of said cup, the mouth of said cupbeing slightly inclined and elongated transversely with respect to thelongitudinal axis of said envelope.

8. A switch of the character described comprising a soft glass envelope,electrodesjand a body of mercury sealed therein, a cuplike elementformed of a substance substantially unaffected by high temperatures orrapid temperature fluctuations and suspended in said envelope from oneof said electrodes and out of contact with the walls of said envelopewhereby upon operation of said switch an alternating mercury to mercurycompletion and interruption of the circuit is obtained at the mouth ofsaid cup, said cuplikeelement housing the free end of said electrode andbeing provided with an elongated extension surrounding and'protectingthe remainder of said electrode.

9. In a mercury switch,a soft'glass envelope, electrodes and mercurysealed therein, and means fixed within said envelope andout of contacttherewith for producing a mercury to mercury make and break intermediatesaid electrodes and confining the same to a location removed from thewalls of said envelope.

11. A mercury switch of the character described including an outerhermetically sealed envelope and means for producing a mercury tomercury make and break within said envelope and within an arcing zonelocated at a point'removed from the walls of said envelope and includinga protective element constituted of a substance substantially unafiectedby high temperatures or rapid temperature fluctuations, said protectiveelement being located within the outer envelope and affording an arcingsurface spaced from the outer envelope, and a support for saidprotective element intermediate the protective element and the outerenvelope and serving to maintain the protective element substantiallyfixed and out of contact with the outer envelope,

while minimizing the transmission of shocks and stresses between theprotective element and the outer envelope.

12. A mercury switch of the character described comprising an outerhermetically sealed envelope, a movable body of mercury therein,electrodes for making contact for said mercury and means for producing amercury .make and break intermediate said electrodes upon bodilymovement of said envelope and including a mercury containing elementseparate from and out of contact with the outer envelopeand fixedlysupported with with the tube and the other terminal.

respect thereto, said mercury containing element being of with one ofsaid electrodes whereby to maintain a portion of the mercury in constantcontact with its associated electrode and to confine the arcing zone toa point on its surface and removed from the. walls of the, outerenvelope whereby to protect the outer envelope and to minimize thetransmissionof shocks and stresses between the outer envelope and thehard glass mercury containing element. a v

13. A mercury switch device comprising an enclosing glass envelope, aninert gas filling, a mercury pool, two electrodes sealed through thewall of the enclosing glass envelope, one of said electrodes interiorlysupporting a refractory element independent of said enclosing glassenvelope, said refractory element being shaped so as to provide meanstherein when the device is in operating position for retaining about oneof said electrodes a part of the mercury as a stationary pool, theremainder of the mercury being retained adjacent the other electrode amovable mercury pool, the flow of which is directed to the saidstationary pool of mercury upon applying to the device a tilting motionin' one direction, and means for definitely effecting the separation ofsaid movable pool of mercury from said stationary pool of mercury uponreturning the device to the original position subsequent to said tiltingmotion.

14. A liquid contact switch comprising a sealed tube containing aquantity of electrical conducting fluid with two electric terminalssealed and supported one above the other in one end thereof and a cup ofinsulating material therein wholly supported by one terminal and havingone terminal entering the interior thereof.

15. A liquid contact switch comprising a sealed tube containing aquantity of electrical conducting fluid with lead-in wires supported andsealed in one end thereof, said lead-in wires projecting as terminalswithin the tube, amp of in sulating material engaged by one terminal andsupported at an angle to the axis of the tube thereby so that the cup isslightly tilted in the direction of the opposite end free from contact16. A liquid contact switch comprising av sealed tube containing aquantity of electrical conducthard glass composition, and associatedrate from the container said container, a

separating said terminal from ing fluid with two electric terminalssealedand supported one abovethe other in one end thereof, and a cup ofinsulating material therein supported by one of said terminalsindependent of' said tube, one of said terminals entering the interiorof the cup.

17. In a mercury switch, the combination with a sealed container, of arefractory. member sepaand supported independently thereof comprising abody having a cavity to holda mercury pool positioned at one end ofmercury body below the edge of said cavity, an electrical conductorincontact with said mercury body, and another electrical conductor incontact with said pool whereby, when the container is tilted, themercury body is, united with said pool at a point located remotely fromthe walls of said container -to electrically connect said conductors.18. The combination with a liquid contact switch of the enclosed typehaving electrodes and a movable body of mercury to bridge saidelectrodes upon a tilting of said switch, of means associated with oneof the electrodes for entrapping a portion of the mercury and holdingthe same in contact therewith to insure a mercuryto-mercury make andbreak upon operation of theswitch, said means being formed ofa substancesubstantially unaffected by high temperatures or rapid temperaturefluctuations and supenvelope, and a refractory member surrounding 1 theterminal of said electrode and supported in fixed relation thereto outof contact and direct connection with the walls of said envelope andserving to entrap a portion of said mercury and hold the same inconstant contact with said terminal to thereby insure; amercury-to-mercury make and break of said circuit over the surface ofsaid refractory member upon operation of said switch.

- 7 PAUL K. CRAMBLET.

